Cooling channel geometry

Abstract

A drilling tool comprising at least one machined groove and at least one web which extend from a tip of the tool to the shank of the tool. A main cutting edge and an inner cooling channel are formed on each web. Said cooling channel extends from the tip to an opposite drill end and has a continuously extending cross-sectional contour enclosing an imaginary circle with a center point. The cross-sectional contour preferably comprises two maximum curvature values whose distance to the drill axis is greater in the direction of a line between the center point and the drill axis or equal to the distance of the center point to the drill axis. Preferably, minimum wall thicknesses exist between the inner cooling channel and (1) the outer periphery of the drill, (2) the machined surface and (3) the non-machined surface, between a minimum and a maximum.

1. A rotary driven cutting tool, comprising a drill having a nominal drill diameter D, at least one spiral cutting groove and at least one land which extend from a tool tip of the drill to a tool shaft of the drill, each land comprising a main cutter and an internal cooling channel which extends from the tool tip to an opposite end of the drill and comprises a continuous cross-sectional contour, which tangentially encloses an imaginary circle with a center, the cross-sectional contour of the internal cooling channel comprising at least one curvature maximum whose distance from an axis of the drill in the direction of a line between the center and the axis of the drill exceeds, or is the same as, the distance between the center and the axis of the drill, a minimum wall thickness between the internal cooling channel and an external circumference of the drill being between a lower limit and an upper limit, a minimum wall thickness between the internal cooling channel and a cutting face of the drill being between said lower limit and said upper limit, and a minimum wall thickness between the internal cooling channel and a cutting flank of the drill being between said lower limit and said upper limit,
 said lower limit being 0.08×D for D<=1 mm, and 0.08 mm for D>1 mm, 
 said upper limit being 0.35×D for D<=6 mm, and 0.4×D−0.30 mm for D>6 mm, 
 a radius at the smallest radius of curvature of the cross-sectional contour of the internal cooling channel corresponding to 0.35 times to 0.9 times a radius of a circle enclosed by the contour. 
 
   
   
     2. The cutting tool according to  claim 1 , wherein the nominal diameter D is within the range of from about 1 mm to about 25 mm. 
   
   
     3. The cutting tool according to  claim 1 , wherein the cutting tool is a two-lip cutter or multiple-lip cutter. 
   
   
     4. The cutting tool according to  claim 1 , wherein the cross-sectional contour comprises two curvature maxima which have substantially identical radial coordinates. 
   
   
     5. The cutting tool according to  claim 1 , wherein the cross-sectional contour comprises two curvature maxima having substantially identical radii of curvature. 
   
   
     6. The cutting tool according to  claim 1 , wherein the cross-sectional area of the cooling channel is symmetrical in relation to a line between the axis of the drill and the center. 
   
   
     7. The cutting tool according to  claim 1 , wherein the cross-sectional contour of the internal cooling channel is elliptical in shape on a side situated towards the cutting face when viewed from a line between the axis of the drill and the center, and/or on a side situated towards the cutting flank, wherein the length ratio between the main axis of the ellipse and the secondary axis of the ellipse is within the range of from about 1.18 to about 1.65. 
   
   
     8. The cutting tool according to  claim 4 , wherein the cross-sectional contour of the internal cooling channel comprises curvature maxima whose distance from the axis of the drill in a direction of a line between the axis of the drill and the center exceeds the distance from the center. 
   
   
     9. The cutting tool according to  claim 8 , wherein the cross-sectional contour of the internal cooling channel on the side facing the cutting face and/or on the side facing the cutting flank radially within the curvature maxima comprises a straight section. 
   
   
     10. The cutting tool according to  claim 9 , wherein the straight sections extend parallel to the cutting face or to the cutting flank. 
   
   
     11. The cutting tool according to  claim 1 , wherein said cutting tool comprises a deep-hole drill with a ratio of nominal diameter D to cutting part length in the range of from about 1:5 to about 1:200.